Rename Vool to Sol

Simple is really the descriptive name for the layer
Sure, it is "virtual" but that is not as important as the fact that it is simple (or simplified)
Also objct (based really) is better, since orientated implies it is a little like that, but only orientated, not really it. Sol only has objects, nothing else
Just cause i was renaming anyway

test/ruby/test_variables.rb

@@ -52,38 +52,38 @@ module Ruby
       assert_equal :Module , lst.name
     end
   end
-  class TestVariablesVool < MiniTest::Test
+  class TestVariablesSol < MiniTest::Test
     include RubyTests
     def test_local_basic
-      lst = compile( "foo = 1 ; return foo").to_vool
-      assert_equal Vool::LocalVariable , lst.statements[1].return_value.class
+      lst = compile( "foo = 1 ; return foo").to_sol
+      assert_equal Sol::LocalVariable , lst.statements[1].return_value.class
     end
 
     def test_instance_basic
-      lst = compile( "@var" ).to_vool
-      assert_equal Vool::InstanceVariable , lst.class
+      lst = compile( "@var" ).to_sol
+      assert_equal Sol::InstanceVariable , lst.class
       assert_equal :var , lst.name
     end
 
     def test_instance_return
-      lst = compile( "return @var" ).to_vool
-      assert_equal Vool::InstanceVariable , lst.return_value.class
+      lst = compile( "return @var" ).to_sol
+      assert_equal Sol::InstanceVariable , lst.return_value.class
     end
 
     def test_class_basic
-      lst = compile( "@@var" ).to_vool
-      assert_equal Vool::ClassVariable , lst.class
+      lst = compile( "@@var" ).to_sol
+      assert_equal Sol::ClassVariable , lst.class
       assert_equal :var , lst.name
     end
 
     def test_class_return
-      lst = compile( "return @@var" ).to_vool
-      assert_equal Vool::ClassVariable , lst.return_value.class
+      lst = compile( "return @@var" ).to_sol
+      assert_equal Sol::ClassVariable , lst.return_value.class
     end
 
     def test_module_basic
-      lst = compile( "Module" ).to_vool
-      assert_equal Vool::ModuleName , lst.class
+      lst = compile( "Module" ).to_sol
+      assert_equal Sol::ModuleName , lst.class
       assert_equal :Module , lst.name
     end